Field of the Invention
The present invention relates to a method of and apparatus for feeding a sheet such as a photographic film, a stimulable phosphor sheet, etc., by smoothly and reliably attracting the sheet with suction cups.
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display device such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation, stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor, or a stimulable phosphor sheet, is stored in a cassette, or a plurality of such stimulable phosphor sheets are stored in a magazine.
The above known system includes an image information reading apparatus which comprises a reading section for reading image information recorded on a stimulable phosphor sheet, and an erasing section for erasing remaining image information from the stimulable phosphor sheet after the recorded image information has been read. In the image information reading apparatus, after a cassette or a magazine (hereinafter referred to as a "cassettes") housing a stimulable phosphor sheet which bears radiation image information of a subject recorded by an external exposure device is inserted into a loading section, the lid of the cassette is opened, and then the stimulable phosphor sheet is taken out of the cassette by a sheet feeding mechanism.
The stimulable phosphor sheet is thereafter delivered to the reading section by a sheet delivering mechanism. In the reading section, a laser beam or the like is applied to the stimulable phosphor sheet to read the recorded image information from the stimulable phosphor sheet. Thereafter, remaining image information is erased from the stimulable phosphor sheet in the erasing section, after which the stimulable phosphor sheet is stored in the cassette from which it has been removed or another cassette in the loading section. The cassette which stores the stimulable phosphor sheet is then removed from the image information reading apparatus.
The loading section does not have a space large enough to allow the cassette to be fully opened because of limitations imposed by the small size of the image information reading apparatus. In the loading section, therefore, the cassette is opened by tilting the lid of the cassette through a predetermined angle. The sheet feeding mechanism moves suction cups along a path which is inclined obliquely downwardly toward the stimulable phosphor sheet in the cassette, causes the suction cups to attract the stimulable phosphor sheet, and then lifts the suction cups to remove the stimulable phosphor sheet from the cassette.
FIG. 21 of the accompanying drawings shows a suction cup 2 as it moves into a cassette which stores a sheet 3. As shown in FIG. 21, when the suction cup 2 moves obliquely downwardly to a surface to be attracted to the sheet 3 as indicated by the arrow X, the leading edge of a skirt 4 of the suction cup 2 obliquely contacts the surface of the sheet 3. Therefore, until the attraction by the suction cup 2 of the sheet 3 is completed, the skirt 4 slips against the surface of the sheet 3. At this time, frictional resistance imposed on the skirt 4 by the sheet 3 tends to deform, e.g., roll, the leading edge of the skirt 4, resulting in a failure to attract the sheet 3 with the suction cup 2.
The above problem is not limited to the arrangement in which the suction cups move obliquely toward and away from the stimulable phosphor sheet. If the suction cups have skirts whose height is larger than the diameter of the suction cups, then the skirts tend to roll on the stimulable phosphor sheet even when the suction cups move perpendicularly toward and away from the stimulable phosphor sheet.
The above system also includes an image information reproducing apparatus for reproducing radiation image information recorded on a stimulable phosphor sheet on a photosensitive medium such as a photographic film. The image information reproducing apparatus has a magazine loading section for loading a magazine which stores a plurality of photosensitive mediums, and a sheet feeding mechanism for removing the photosensitive mediums, one by one, from the magazine that is loaded in the magazine loading section. The sheet feeding mechanism has suction cups which suffer the same problem with respect to the photosensitive mediums as the problem described above with respect to the suction cups and the stimulable phosphor sheets in the image information reading apparatus.
Attempts have heretofore been made to solve the above problem by making suction cups of a slippery material or roughening the attracting surfaces of suction cups to make them slippery. However, if the suction cups are made slippery, then the frictional resistance between the suction cups and the sheet becomes smaller than required. Specifically, when the slippery suction cups move while attracting the sheet, the sheet is liable to be positionally displaced relatively to the suction cups, or fall off the suction cups.